If you are heading for the coast this summer - keep an eye out for jellyfish.

Billions of the billowing creatures are swimming in our seas in what scientists say is an exceptional year for the animals.

A new study by the Marine Conservation Society and the University of Exeter found that last year saw record numbers of jellyfish.

This year is likely to be just as good, according to data collected by volunteers across the country.

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A study by the Marine Conservation Society and University of Exeter found record numbers of jellyfish in British waters last year and this year is expected to be the same. Pictured: A jellyfish spotted at St Mawes, Cornwall

The new report, published in the Journal of the Marine Biological Association, also maps concentrations of jellyfish by species and location for the first time in 40 years, using data collected over the last decade.

It finds that numbers are particularly high off the coasts of Cornwall, Devon and south Wales, especially for species such as the spectacular four-foot long barrel jellyfish.

Dr Peter Richardson, biodiversity programme manager for the MCS, said: ‘In parts of the South West it is absolute jellyfish soup right now.

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The survey found that only three of the five most common jellyfish sting humans, but Dr Richardson said there are other important impacts to consider.

In recent years vast influxes of the creatures have been known to wipe out salmon farms, and in 2011 they forced Torness power station in Scotland to close after they clogged up its machinery.

Dr Richardson added: ‘We can’t afford to ignore the costs to the environment of an increase in jelly-fish.’

‘It can affect tourism, it can affect power generation, it can affect fishing. That is why we have started this process of mapping hot spots of jellyfish, when and where they appear.’

Known as the ‘barometer of the seas’, the animals are incredibly sensitive to changes in temperature, pollution and predators.

But scientists are divided as to the conditions that cause increase in populations.

In some years hot weather can cause a fluctuation of jellyfish, but in others it does not.

Some think that tides and winds have an impact, with water funnelled up into the Celtic and Irish Seas, drawing billions of animals into British waters.

Prof Brendan Godley of the University of Exeter said: ‘The remarkable number of barrel jellyfish re-ported from South West England this year is quite unusual.

‘We’re not sure why, but the very mild winter probably meant more adults survived at depth, which will have returned to the surface in spring as waters warmed up.

‘This year’s strange barrel jellyfish results highlight the importance of running the survey year in and year out to track these unusual events and discover if they turn into trends.’

Last year proved a record year when 1,133 reports of jellyfish were received around the country.

This year already 500 reports already received by mid-July, only halfway through summer months when most records are received.

The moon jellyfish, a transparent
umbrella-shaped species, was the most frequently-spotted species around
the UK coast, as well as being the most widely-distributed.

This huge barrel jellyfish was found washed up on a beach in Portland, Dorset earlier this year

Other common sightings were for compass, lion’s mane, blue and barrel jellyfish.

The other species are the mauve stinger, Portuguese Man of War and the by-the-wind sailor, which are sporadic visitors to British coasts.

Dr Richardson added: ‘We still know relatively little about jellyfish, but given the economic impacts that large numbers of jellyfish can have on tourism, fishing, aquaculture and even power generation, we can’t afford to ignore them.’

Prof Godley said: ‘By taking stock of our jellyfish in this way, we provide an important baseline of in-formation which will help us understand how jellyfish species react to environmental changes that influence our coastal seas, including climate change.’